Question

During crossing, why do new features which are not present in the parents appear in the offsprings?

Answer 1

Parent genes normally have pure genes , when they are crossbred you get the f1 progeny ,here the dominant characters like tall is expressed whereas the short is not .In  the offsprings both the short and tall traits are expressed where most of the plants are tall.

to summarise the parents have all the traits but only the dominant traits are expressed.

hope you understood.